Figure 810

Biopsy results in the Madrid acute renal failure (ARF) study. Kidney biopsy has had fluctuating roles in the diagnostic work-up of ARF. After extrarenal causes of ARF are excluded, the most common cause is acute tubular necrosis (ATN). Patients with well-established clinical and laboratory features of ATN receive no benefit from renal biopsy. This histologic tool should be reserved for parenchymatous ARF cases when there is no improvement of renal function after 3 weeks' evolution of ARF. By that time, most cases of ATN have resolved, so other causes could be influencing the poor evolution. Biopsy is mandatory when a potentially treatable cause is suspected, such as vasculitis, systemic disease, or glomerulonephritis (GN) in adults. Some types of parenchymatous non-ATN ARF might have histologic confirmation; however kidney biopsy is not strictly necessary in cases with an adequate clinical diagnosis such as myeloma, uric acid nephropathy, or some types of acute tubulointerstitial nephritis . Other parenchymatous forms of ARF can be accurately diagnosed without a kidney biopsy. This is true of acute post-strepto-coccal GN and of hemolytic-uremic syndrome in children. Kidney biopsy was performed in only one of every 16 ARF cases in the Madrid ARF Study [1]. All patients with primary GN, 90% with vasculitis and 50% with secondary GN were diagnosed by biopsy at the time of ARF. As many as 15 patients were diagnosed as having acute tubulointerstitial nephritis, but only four (27%) were biopsied. Only four of 337 patients with ATN (1.2%) underwent biopsy. (Data from Liano et al. [1].)

* One patient with acute-on-chronic renal failure.

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